In the art of emulsions adapted to form films and coatings, mixed polymer and interpolymer emulsions utilizing an alkyd resin have heretofore been prepared typically by following either one of two different procedures. By one procedure, separately formed but compatible dispersions or solutions of, respectively, an alkyd resin on the one hand, and a compatible emulsion of polymerized vinyl monomer on the other hand are simply admixed together. By the other procedure, a preformed solution or dispersion of alkyd resin has incorporated thereinto an appropriate emulsifier and then selected vinyl monomers are added thereto and emulsion polymerized in situ so as to provide an interpolymer system.
Regardless of the method of preparation, to prepare a paint, the resulting emulsion system is typically additionally formulated with pigments, curing agents, perhaps additional emulsifiers, and other additives, so that the product system is typically a complex system in which the various components are carefully and even critically balanced against one another in type and quantity so as to provide commercially acceptable latex paints. Such a paint suffers from various disadvantages. For one thing, the very complexity of such conventional prior art paint systems is disadvantageous from a cost of preparation standpoint. For another thing, the presence of an emulsifier in a product painted surface prepared from such an emulsion system is usually subject to problems, such as disadvantages arising from retained water sensitivity of the dried films, as manifested, for example, in water spotting, in leaching of the emulsifiers when films are sprinkled with water, with subsequent film streaking, and in reduced film water and scrub resistance. Ideally, the art would like to have stable emulsions which combine the advantages of alkyd resins and of emulsion polymerized vinyl-type monomers without using conventional emulsifiers and which produce improved coating characteristics.
Herefore, an effort has been made to disperse a pigment in an alkyd resin dispersion so as to form a paint and then to polymerize in situ vinyl monomers in this paint. This procedure of prepigmenting has generally not been commercially promising because, as the quantity of pigment is increased to levels commonly employed in commercial paints, the ability to conduct emulsion polymerization in the resulting prepigmented alkyd system decreases. In such prepigmented system, the choice of components is apparently critical so that only a limited variation in components and reactants is possible in a system at the time of vinyl monomer emulsion polymerization. Also, in such a prepigmented system, the resulting system after polymerization of vinyl monomer therein appears to have relatively poor stability characteristics.
So far as is known, no one in the art has ever heretofore prepared interpolymer emulsions comprising a preformed alkyd resin and in situ polymerized vinyl monomers without using a conventional emulsifier.